1. Field of the Invention
The present invention relates to active ingredients of cosmetic or dermatological preparations for the prophylaxis and treatment of inflamed skin conditions and/or skin protection in dry skin determined to be sensitive.
Furthermore the invention relates to the use of such active ingredients and preparations containing such active ingredients for the immunostimulation of the skin, thereby advantageously also for immunostimulation in terms of a treatment of injured skin, in particular for the treatment of wounds.
Moreover, the invention relates to preparations with extremely low so-called “stinging potential” and cosmetic or dermatological formulations that care for the skin—e.g., after sun-bathing—in a targeted manner and reduce the after reactions of the skin to the action of UV radiation.
2. Discussion of Background Information
The skin, in particular the epidermis, as the barrier organ of the human organism, is subjected to a particular extent to external influences. According to current scientific knowledge, the skin represents an immunological organ that as an immunocompetent peripheral compartment has its own role in inductive effective and regulative immunological processes of the organism in its entirety.
The epidermis is richly equipped with nerves and peripheroceptors such as lamellated corpuscles, Merkel cell neuritic complexes and free nerve endings for pain sensation, cold sensation, heat sensation and itching.
Immunosuppression in general is the suppression or reduction of the reactivity of the immune system. Immunosuppression can be divided into local and systemic effects. Ultimately it covers a plurality of different aspects that all include a reduction of the normal immunological defense mechanisms of the skin. It is known that ultraviolet (UV) light, as is contained in sunlight, can lead to immunosuppression. In the irradiation of the skin with UV light (in particular UVB light) both local and systemic aspects of UV-induced immunosuppression are observed (<Engl.> “to sting”=to injur, burn, be painful).
In people with delicate, sensitive or easily injured skin, a neurosensory phenomenon known as “stinging” can be observed. This “sensitive skin” is fundamentally different from “dry skin” with thickened and hardened horny layers of the epidermis.
Typical reactions of “stinging” with sensitive skin are reddening, tightening and burning of the skin, as well as itching.
“Stinging” phenomena can be considered disorders that are to be treated cosmetically. In contrast, severe itching, in particular with severe itchy skin occurring with atopy and itching with skin diseases, can also be labeled as a more serious dermatological disorder or a neurosensory phenomenon.
Typical disturbing neurosensory phenomena associated with the terms “stinging” or “sensitive skin” are reddening of the skin, tingling, prickling sensation, tightening and burning of the skin and itching. They can be caused by stimulating environmental conditions, e.g., massage, effect of (detergent) surfactants, weather influence, such as sun, cold, dryness, as well as humid heat, thermal radiation and UV radiation, e.g., by the sun.
In the Journal of the Society of Cosmetic Chemists, 28, p. 197-209 (May 1977) P. J. Frosch and A. M. Kligman describe a method of estimating the “stinging potential” of topically applied substances. As positive substances, e.g., lactic acid and pyruvic acid are used here. In measuring according to this method, however, amino acids, in particular glycine, were also determined to be neurosensorily active (such substances are called “stingers”).
According to previous findings, such a sensitivity to particular substances occurs differently from individual to individual. This means that a person who experiences a “stinging effect” on contact with a substance, will in all probability experience it again on each further contact. However, contact with other “stingers” is just as likely to occur without any reaction.
Many more or less sensitive people also suffer from erythematous skin conditions at the use of some deodorizing or antiperspirant preparations.
Furthermore, erythematous skin conditions also occur as concomitant symptoms with certain skin diseases or irregularities. For example, the typical rash in the external manifestation of acne is regularly more or less severely reddened.
In people sensitive thereto, also shaving induces erythema, burning, itching and tightening that are caused by the superficial injury and the mechanical stress of the upper dermal layers with both wet shaving and dry shaving. These symptoms often occur with the daily shaving of the beard, but irritation can also occur after shaving armpits, bikini line and legs.
In addition to the positive effects of sunlight, such as general well-being, the formation of vitamin D3 and acne treatment, there are also negative effects that should be combated.
The conditions of sunbathing represent an unaccustomed—in part extreme—strain on the human organism by which the skin in particular is affected. As long as the radiation stress does not exceed a certain level, our skin can cope with it. Slighter damage, as is present in imperceptible suberythema, is repaired immediately.
However, if the skin is exposed for too long to the sun or an artificial source of radiation, after a latency period of 2 to 3 hours a reddening of the skin that is very distinguishable from the non-irradiated skin develops, the erythema solare. With the sunburn that thus occurs a distinction is made between                1st degree: erythema (reddening, feeling of warmth, burning, tightening of the skin) subsides again after 2 to 3 days and disappears with simultaneously increasing pigmentation,        2nd degree: blistering blisters form on the skin with burning and itching, the epidermis is sloughed extensively        3rd degree: cell damage deep cell damage occurs, the body reacts with raised temperature, the epidermis is sloughed very extensively.The 2nd and 3rd degrees are also called solar dermatitis.        
The formation of the erythema depends on the wavelength. The erythema range of UV B is between 280 nm and 320 nm.
Approximately 90% of the ultraviolet radiation reaching the earth is made up of UV A rays with a wavelength of between 320 nm and 400 nm. Whereas the UV B radiation varies greatly depending on numerous factors (e.g., time of the year and time of the day or degree of latitude), the UV A radiation remains relatively constant day by day regardless of the time of year or the time of day or geographical factors. At the same time most of the UV A radiation penetrates the living epidermis, whereas about 70% of the UV B radiation is stopped by the horny layer of the epidermis.
For a long time it was mistakenly assumed that the long-wavelength UV A radiation has only a negligible biological effect and that accordingly the UV B rays are responsible for most light damage to the human skin. However, in the meantime it has been proven by numerous studies that UV A radiation is much more dangerous than UV B radiation in terms of triggering photodynamic, specifically phototoxic reactions and chronic changes to the skin. The damaging effect of UV B radiation can also be further increased by UV A radiation.
Since the contributions of the various wavelength ranges of UV light to changes in the skin caused by light have not been fully determined, today it is increasingly assumed that preventive protection against both UV A and UV B rays, e.g., through the application of sunscreen filter substances in the form of a cosmetic or dermatological formulation on the skin, is of fundamental importance. Cosmetic or dermatological means, applied to the skin in a thin layer, are to protect the skin from the negative effects of solar radiation.
Most people find sunbathing pleasant and at first do not consider the disadvantageous effects. However, in recent years an awareness has certainly developed about the negative effects of too intensive an exposure to sunlight, which is why more sunscreens and sunscreens with greater protection are being used.
Sunburn or photo-erythema are the acute manifestations of the effect of light. In addition to the effects of UV rays already described, in the after reaction of the skin a reduced production of sebum and a drying of the skin also occur. So-called after-sun preparations are used to treat the skin, the application of which is on principle recommended after each exposure to the sun. These are as a rule emulsions or aqueous hydrogels that in addition to conventional moisturizing substances can also contain special active ingredients, such as, e.g.:                anti-inflammatory and cooling substances,        locally anesthetizing substances and/or        disinfecting substances in order to prevent possible skin infections.        
Anti-inflammatory active ingredients extracted, e.g., from plants, such as azulene and bisabolol (chamomile), glycyrrhizin (licorice root), hamamelin (witch hazel) or whole extracts, e.g., from aloe vera or chamomile are used. With lighter forms and locally limited erythema reactions, these show some success. The same applies to creams with a high content of essential oils or panthenol.
After sun preparations are intended to cool the skin after sunbathing and to improve its humectant capacity, whereby conveying the cooling effect has a central role. This cooling effect is achieved, e.g., by high quantities of ethanol that evaporates spontaneously on the application of the formulation to the skin. As a result of the cold due to evaporation of the aqueous phase, hydrogels, o/w emulsions (lotions) or aqueous lotions also have a pronounced cooling effect that leads to an alleviation of the inflammation through a local vascoconstriction.
The object of the present invention was to overcome the disadvantages of the prior art and to provide active ingredients and preparations containing such active ingredients for the cosmetic and dermatological treatment and/or prophylaxis of erythematous, inflammatory, allergic or auto-immune reactive symptoms, in particular dermatoses, but also of the manifestation of “stinging.”
Furthermore, such active ingredients or preparations containing such active ingredients were to be provided which can be used for the immunostimulation of the skin, thereby also advantageously for immunostimulation in the sense of the effect of promoting wound healing.
The term “inflammation” is a relatively extensive and old term. Even before Christ, Aulus Celsus introduced four of the five cardinal signs of inflammation: rubor, tumor, calor and dolor (reddening, swelling, heat and pain). In the second century Galen of Pergamon defined the fifth sign: functio laesa (restricted function). In all, inflammation research has been going on for 2000 years, 200 years of them at cellular level and 20 years at molecular level. It has thereby become more and more obvious that the term is nonuniform.
Inflammatory disorders are characterized by infiltrates of inflammatory cells, which, however, can be composed very differently. Psoriasis, an inflammatory skin disorder, is, e.g., characterized by an infiltrate of oligoclonal T cells and polymorphonuclear granulocytes in sharply defined inflammatory plaques. The involved skin of the atopic eczema, however, is characterized by infiltrating T cells against environmental antigens and eosinophilic granulocytes. The therapies with anti-inflammatory substances are equally as diverse as the inflammatory manifestations.
It cannot by any means be assumed that a substance that shows a very good effect with one inflammatory disorder will also have the same effect with other inflammations. Intensive research is therefore being conducted in this field, many of these usually chronic disorders are still impossible to treat satisfactorily. Adrenocortical steroids come closest to such an all-embracing effect, but because of the in part serious side-effects they cannot be considered for a continuous and lengthy application. Adrenocortical steroids are even completely banned for cosmetic applications for this reason, other substances have to be used here.
Cosmetics for soothing the skin are used with acute skin irritations; these are to be distinguished from the (chronic) inflammations described above. The cause of irritations can be, e.g., physical stimuli such as UV radiation or shaving. In particular in the early stage and with a slight degree of stimulus, there is no infiltrate of inflammatory cells (T cells, macrophages, granulocytes, . . . ), instead the affected skin cells (mainly keratinocytes and fibroblasts) themselves produce an abundance of pro-inflammatory mediators. These mediators activate the cells, induce defense and repair mechanisms and subsequently attract inflammatory cells. The object of the soothing effect on the skin of cosmetics must therefore be to prevent the negative consequences of the irritation, without blocking the necessary repair mechanisms. The known anti-inflammatory substances that are to act above all on the infiltrating cells can therefore only be used to a limited extent as model substances.
It was surprising and therein lies the solution to these objects, that the use of licochalcone A or in cosmetic preparations for the care and/or alleviation of erythema caused by physical irritation of the skin would overcome the disadvantages of the prior art.